Production of citric acid by submerged fermentation. Effect of medium sterilisation at pilot-plant level

In large-scale fermenters, in situ sterilisation takes a long time and there is probably thermal degradation of the medium constituents, the products of which generally affect the final yield. Sterilisation cycles were designed according to the microbial load in the broth and their effect on the production of citric acid studied in 4-m3 fermenters. It was found that the medium could tolerate Del values up to 48 against a calculated value of 35.50. Above this value there was thermal degradation of the medium constituents which adversely affected the morphology of the fungus Aspergillus niger, and consequently the citric acid yields.